Major Revision; Completed 1-way sync #19 #47

Huge changes to deleting tasks.
If Task has no Google ID, delete task as usual.
If Task has Google ID, delete task will not remove from the storages
UNTIL a successful delete from Google is applied. Meanwhile, these
tasks will be marked as isDeleted = true.

Updated FilterTasks to NOT display tasks that have isDeleted flag set
as true.
Updated FilterTasks with new method hideDeleted(List<Task>) to
automatically hide tasks with isDeleted=true.

Updated ConcurrentDelete to the task’s Google ID to empty after it is
deleted from Google.

Updated DisplayView to use the Filtered List
(FilterTasks.getFIlteredList();) upon init instead of
StorageHandler.getAllTasks().